Naloxone in chronic schizophrenic patients: neuroendocrine and behavioral effects

Opioid antagonists are associated with a reduction in the symptoms of schizophrenia: a meta-analysis of controlled trials

Current treatments for the symptoms of schizophrenia are only effective for positive symptoms in some individuals, and have considerable side effects that impact compliance. Thus, there is a need to investigate the efficacy of other compounds in treating both positive and negative symptoms. We conducted a meta-analysis of English language placebo-controlled clinical trials of naloxone, naltrexone, nalmefene, and buprenorphine in patients with schizophrenia to determine whether opioid antagonists have therapeutic efficacy on positive, negative, total, or general symptoms. We searched online databases Ovid Medline and PsychINFO, PubMed, EMBASE, Scopus, Cochrane library/CENTRAL, Web of Science, and Google Scholar from 1970 through February 2019. Following PRISMA guidelines, Hedges g was calculated for each study. Primary study outcomes were the within-subject change on any symptom assessment scale for positive, negative, total, or general symptoms of schizophrenia between active drug and placebo conditions. Thirty studies were included with 434 total patients. We found a significant effect of all drugs on all scales combined with both a standard random effects model: (g = 0.26; P = 0.02; k = 22; CI = 0.03-0.49) and a more inclusive bootstrap model: (g = 0.26; P = 0.0002; k = 30; CI = 0.11-0.51) and a significant effect on total scales with the bootstrap model (g = 0.25288; P = 0.015; k = 19; CI = 0.04-0.35). We also observed a significant effect of all drugs on all positive scales combined with both the random effects (g = 0.33; P = 0.015; k = 17; CI = 0.07-0.60) and bootstrap models (g = 0.32; P < 0.0001; k = 21; CI = 0.13-1.38). This evidence provides support for further testing in randomized clinical trials of a new class of non-D2-receptor drugs, based on opioid mechanisms, for the treatment of positive and negative symptoms of schizophrenia.

The Role of Dynorphin and the Kappa Opioid Receptor in the Symptomatology of Schizophrenia: A Review of the Evidence

Schizophrenia is a debilitating mental illness that affects approximately 1% of the world's population. Despite much research in its neurobiology to aid in developing new treatments, little progress has been made. One system that has not received adequate attention is the kappa opioid system and its potential role in the emergence of symptoms, as well as its therapeutic potential. Here we present an overview of the kappa system and review various lines of evidence derived from clinical studies for dynorphin and kappa opioid receptor involvement in the pathology of both the positive and negative symptoms of schizophrenia. This overview includes evidence for the psychotomimetic effects of kappa opioid receptor agonists in healthy volunteers and their reversal by the pan-opioid antagonists naloxone and naltrexone and evidence for a therapeutic benefit in schizophrenia for 4 pan-opioid antagonists. We describe the interactions between kappa opioid receptors and the dopaminergic pathways that are disrupted in schizophrenia and the histologic evidence suggesting abnormal kappa opioid receptor signaling in schizophrenia. We conclude by discussing future directions.

Clinical relevance of endorphins in psychiatry

1. 13 years after the discovery of endorphins, the relationships between these peptides and mental illness remain unclear. 2. Current concepts are controversial and convincing hypotheses have not been elaborated yet. 3. Endorphin measurements in CSF or serum of psychiatric patients did not strongly support that schizophrenia or depression is related to a deficit or an excess of these peptides. Moreover, treatment with endorphins or opiate antagonists did not result in a distinct change of psychiatric symptoms. Recently, research focused on the relationship between endorphins and addictive behavior, but substantial evidence for clinical relevance is still missing. 4. The physiological relevance of many newly discovered endorphins is barely known and several subtypes of the opiate receptor have been found. Thus, it will still require a substantial effort in basic and clinical studies before, if at all, endorphins turn out to be helpful in the treatment of mental illness.

Multiple hormonal responses to morphine: relationship to diagnosis and dexamethasone suppression

Plasma cortisol, prolactin (PRL), growth hormone (GH), and thyroid stimulating hormone (TSH) responses to intravenous morphine (0.1 mg/kg body weight) were investigated in five healthy women and 22 female psychiatric inpatients (eight with major depression, 12 with schizophrenia and two with personality disorders) during a 120 min period. The results were also related to a subsequent dexamethasone suppression test (DST). Morphine caused a strong and progressive decline in plasma cortisol which was uniform in controls, depressed, and nondepressed patients. DST nonsuppressors had significantly higher cortisol levels during the entire period, but the same response to morphine. Morphine strongly stimulated PRL secretion, which was found to be significantly smaller in patients than in controls, but no difference was seen between depressed and nondepressed subjects. GH and TSH showed only minor and variable changes after morphine, with no overall significant differences. The data in this study do not support the assumption of a major alteration in opiate receptor responsivity either in depression or in DST nonsuppressor patients insofar as the regulation of the adrenal, thyroid, GH and PRL hormone secretion is concerned.

Overview of drugs used in treating drug-induced dependence: a treatise interrelating existing hypotheses in order to attain maximal therapeutic benefits

Despite the fact that we do not yet completely understand the physiology of physical dependence, many treatment modalities are available. In this overview, an attempt is made to discuss available treatments and mechanisms to possibly attain a better understanding of the complex interactions that occur between systems. An attempt is also made to understand interrelations between drug misuse and mental disorders as one aspect of the treatment process--the ultimate goal being more efficacious and safer therapy.

Sensory symptoms in Parkinson's disease and the opioid system

Primary sensory symptoms not related to somatic disease, are often experienced by patients with Parkinson's disease. These subjective sensations may either accompany or precede the motor disorder. This paper provides evidence supporting a role for the endogenous opioid system in the pathogenesis of sensory symptoms in Parkinson's disease.

Repeated naloxone administration in schizophrenia

A double-blind study of repeated subcutaneous administrations of 20 mg naloxone was performed in 10 schizophrenic patients as part of a World Health Organization collaborative project. No clinically obvious treatment effects were observed. None of the analyzed psychopathological symptoms, including hallucinations and unusual thought content, showed a distinct improvement during the 4 consecutive days of naloxone treatment. A slight but statistically significant decrease of symptomatology was found shortly after placebo injection on the first 2 days of treatment. This effect was not present following naloxone treatment. These findings are discussed in view of the hypothesis that increased endorphin activity contributes to the symptomatology of schizophrenic syndromes.

Endogenous opiates: 1982

This article is the fifth installment in an annual series of reviews of successive year's research dealing with the endogenous opiate peptides. Due to the continuing massive increase in the number of studies in this field, it has become impossible to continue comprehensive reviews of all aspects of this work. As a result we have decided that beginning this year the coverage will be abbreviated to emphasize non-analgesic and behavioral work. The specific areas discussed include stress, tolerance and dependence, consummatory responses, alcohol consumption, schizophrenia and emotional disorders, learning and memory, cardiovascular responses, respiratory effects, thermoregulatory effects, neurological deficits and other disorders, activity, and other, miscellaneous behaviors. As in previous years, we have attempted a relatively comprehensive review of the subjects covered only for the previous year and have not made an attempt to evaluate their contributions relative to those of past years.

Neuroendocrine effects of endogenous opioid peptides in human subjects: a review

In the decade since the discovery of specific opioid receptors in the brain, there have been rapid advances in our understanding of the physiological and pathological roles of the endogenous opioid systems in humans. Endogenous opioid peptides have been demonstrated to play a role as modulators of a number of hormonal functions in humans. In particular they appear to inhibit luteinizing hormone and ACTH release, and the response of arginine vasopressin to osmotic stimuli. They appear to participate in the modulation of carbohydrate homeostasis. In pathophysiological states, they appear to play a role in the decreased pulsatile luteinizing hormone release seen in patients with prolactinomas. Circulating beta-endorphin appears to be an important regulator of immune function. Preliminary studies in humans have suggested a role for endogenous opioid peptides in appetite regulation. In the last few years, a few case reports have suggested the possibility of a series of syndromes due to endogenous opioid excess. Within the next decade, we can expect to see the routine use of opioid antagonists in a variety of pathophysiological states.